"additional grunt" means having extra strength, power, or effort to get a job done. It implies having additional resources or ability to achieve something. Full definition
Guns however are the key to surviving Revelations and players can upgrade these items for additional grunt. (impulsegamer.com)
The 3.2 - liter V - 6 isn't as smooth as some of its rivals, but it emits a throaty growl at the top end and provides meaningful torque from as low as 2500 rpm, with additional grunt above 4000. (automobilemag.com)
The better news for both the Mini Cooper and Cooper S is that new, BMW - sourced engines provide enough additional grunt to easily obliterate any additional pounds. (automobilemag.com)